Rolling bearing

Abstract

An object of this invention is to provide a rolling bearing which is long enough in serve life even when it is applied with a lubricant mixed with foreign matters, simply by quenching or by carbonitriding it for a short period of time, and which can be formed at a relatively low manufacturing cost. A rolling bearing is formed as follows: The quantities of elements such as C, Si, Mn, Cr and Mo forming a bearing alloy steel, and the quantity of retained austenite are adjusted to be in predetermined ranges, and the steel is quenched and tempered or carbonitrided so that its hardness is in the following range: -2.2×(γ.sub.R vol %)+810≦Hv≦-2.2×(γ R vol %)+930

What is claimed is: 
     
       1. A rolling bearing comprising bearing rings and rolling elements which roll between said rings, wherein: at least one of said bearing rings and rolling elements are made of an alloy steel which contains, C 1.1 to 1.6% by weight,   Si 0.05 to 0.8% by weight,   Mn 0.5 to 1.5% by weight, and   Cr 1.3 to 3.0% by weight;     the quantity of austenite retained in the surface layer of at least one of said bearing rings and rolling elements being 13 to 40% by volume in said bearing rings and/or rolling elements which have been subjected to a heating treatment in a coexistence region of austenite and carbide in a Fe--C equilibrium diagram, and then also are subjected to a tempering treatment;   a carbide area ratio of retained carbide retained in the surface layer of said bearing rings and/or rolling elements after being subjected to said heating treatment and said tempering treatment being in the range of 8-22%; and   the hardness (Hv) of said bearing rings and/or rolling elements after being subjected to said heat treatment and said tempering treatment being in the following range with respect to said quantity of retained austenite (γ R ):   -2.2×(γ.sub.R vol %)+810≦Hv≦-2.2×(γ.sub.R vol %)+930.       
     
     
       2. A rolling bearing according to claim 1, wherein said heat treatment is a quenching treatment in which said quantity of austenite retained in the surface layer thereof is 13 to 20% by volume. 
     
     
       3. A rolling bearing according to claim 1, wherein said heat treatment is a carbonitriding treatment and a quenching treatment in which Si contents are 0.05 to 0.45% by weight. 
     
     
       4. A rolling bearing according to claim 1, wherein said alloy steel further contains Mo 0.6% or less by weight. 
     
     
       5. A rolling bearing according to claim 2, wherein said alloy steel further contains Mo 0.6% or less by weight. 
     
     
       6. A rolling bearing according to claim 3, wherein said alloy steel further contains Mo 0.6% or less by weight. 
     
     
       7. A rolling bearing according to claim 3, wherein said quantity of austenite retained in the surface layer thereof is 17 to 30% by volume. 
     
     
       8. A rolling bearing according to claim 3, wherein said alloy steel further contains Mo 0.6% or less by weight and said quantity of austenite retained in the surface layer thereof is 17 to 30% by volume. 
     
     
       9. A rolling bearing according to claim 3, in which said carbonitriding treatment is conducted in an atmosphere of Rx gas, enriched gas and 5% ammonia gas.